In the parched and seemingly lifeless heart of the Sahara desert, earthworms find enough moisture to survive. Four major mountain ranges interrupt the flow of dunes and gravel plains, and at certain
Marq de Villiers?and Sheila Hirtle are coauthors of Sahara: The Extraordinary History of the World's Largest Desert and several other books on exploration, history, politics, and travel. Sable Island,
